Digital subscriber line (DSL) technology allows for high-bandwidth networking connections to be made over ordinary copper telephone lines. Traditional phone service typically relies on unshielded twisted pair (UTP) copper lines to connect homes and small businesses to the communications network operated by the telephone company (TELCO). Every one of these networks includes a central offices (CO) that services a defined region, with each CO responsible for connecting and routing calls directed to sites that reside both internal to and external of the network.
Branching out from the central office are numerous remote terminals (RT) located throughout the region being served by the CO, with each RT providing the phone service for the subscribers located within a specific area or neighborhood. One of the primary components that make up a remote terminal (RT) is a pair gain system, also known as a derived carrier system, or digital loop carrier system. In simplest terms, the pair gain system provides the TELCO with the capability to carry multiple services over a lesser number of lines, for example, five conversations over one telephone line. The pair gain system also is responsible for generating the dial tone signal one hears when they first pick up a telephone handset, indicating that an active connection is present.
FIG. 1 depicts a typical telephone connection between a pair gain system 10 of a remote terminal (RT) (not shown) and a subscriber 30. As indicated in FIG. 1, the connection between the pair gain system 10 and subscriber 30 is not accomplished directly, but instead in two legs. The first connection 10a exists between the pair gain system 10 and a cross connect block 20, while the second connection 20a is made between the cross connect block 20 and a subscriber 30. As indicated by its name, the purpose of the cross connect block 20 is to allow easy matching and connecting of two or more connections to one another, thereby facilitating the addition or removal of phone services to or from the subscriber.
To further illustrate the use of a cross connect block 20, consider the following example involving a typical modern day residence. New homes are often pre-wired to handle multiple telephone lines, i.e. six lines, to allow for future expansion. In this situation, there would be six connections running between the subscriber's house 30 and the cross connect box 20. However, if the subscriber only has two active phone lines, then only two connections representing the active circuits would run from the pair gain system 10 to the cross connect box 20. Later, if the subscriber wishes to add a new telephone line for a fax machine, a technician would have to run a new connection between the pair gain system 10 and the cross connect block 20, matching the new connection at the cross connect block 20 to the appropriate connection already present that runs to subscriber's house 30.
Note that each of connections 10a and 20a, along with the connections discussed below, although drawn as single lines in the figures, actually represent a cable pair, such as, for example, typical unshielded twisted pair (UTP) copper lines. For the remainder of the application, the terms “connection” and “cable pair” should be considered interchangeable. In view of this, it should be further understood that terminals for receiving these connections, such as can be found on cross connect block 20, are comprised of two conductors, with each conductor receiving one cable of the cable pair.
FIG. 2 depicts the same connection as previously depicted in FIG. 1. However, unlike the previous depiction, FIG. 2 provides a more detailed illustration of cross connect block 22, which is illustrated as an insulation-displacement connection (IDC) block. Unlike blocks that rely on screw-terminals or a wire wrapping technique to secure wires to the block, IDC blocks provide for a gas-tight connection without requiring the removal of insulation covering the wire. Connection is achieved once a wire is placed into an IDC block contact, and then punched down, typically via an insertion tool, pressing the wire against the contact to form the gas-tight connection. Due to ease of use and effectiveness, cross connect blocks utilizing IDC contacts have become the standard within the telecommunications industry.
As DSL technology is relatively new compared to typical telephonic communication involving analog signals, many of the remote terminals (RT) that are part of a telephone company's (TELCOs) network were not designed to allow easy incorporation of newer technology such as DSL. Accordingly, the TELCOs have had to develop ways to effectively provide DSL service to their subscribers utilizing the existing equipment on the network.
FIG. 3 depicts a typical approach to incorporating DSL service with a remote terminal (RT). The dial tone signal generated by the pair gain system 10 is directed to a splitter 50 via connection 10a. Splitter 50 also receives a connection 40a from a DSL system 40. DSL system 40 includes the equipment necessary for processing and directing the data signals back and forth between subscriber 30 and a digital subscriber line access multiplexer (DSLAM) (not shown). The DSLAM, which is operated by a service provider, takes all of the subscribers' DSL connections and aggregates them onto a single, high-density connection to the Internet. For the current illustrative example involving the integration of DSL at an RT, the DSL system may be physically mounted inside the cabinet housing the RT, or placed in its own cabinet mounted onto or next to the RT depending on factors such as size limitations and ease of access.
The role of splitter 50 is to combine the lower frequency signal from the pair gain system 10 with the higher frequency DSL data signal in such a way that they don't interfere with one another. Similarly, splitter 50 must also be capable of separating the signal sent by the subscriber 30 back into its two constituent components and then direct them back to the appropriate system. In FIG. 3, splitter 50 is depicted as an independent component separate from DSL system 40. Alternatively, splitter 50 may be incorporated into DSL system 40.
The combined signal produced by splitter 50 is delivered to cross connect block 20 over connection 50a, where it is then directed to subscriber 30 over connection 20a. Subscribers 30 can then access the higher frequency DSL signal by means of a DSL modem connected between their computing device and the telephone line(s) running throughout their residence. At the same time, standard telephones continue to have access to the lower frequency analog signals also routed over the line(s).
To accomplish the arrangement illustrated in FIG. 3, a service technician is required to go onsite and perform wiring locally at the remote terminal (RT) that is servicing the subscriber. In order to combine the signal coming from the pair gain system 10 with the DSL data signal, the pair gain system 10 that normally is directly wired to cross connect block 20 must now be rerouted so that it interfaces with splitter 50. At splitter 50, the signal from the pair gain system 10 is combined with the DSL data signal, which also runs through splitter 50. The combined dial tone and DSL signal must then be placed back into communication with subscriber 30, requiring a new connection between splitter 50 and cross connect block 20. Due to these re-wiring requirements, the telephone service of subscriber 30 is disrupted; preventing them from making or receiving any telephone calls. Further, the duration of this disruption can vary depending on the knowledge and skill of the service technician, along with the condition of the RT.
If a DSL subscriber decides he or she no longer wants DSL service, the service technician must access the remote terminal (RT) again and disrupt the connection 40a that provides communication between the DSL system 40 and splitter 50. The splitter 50 must also be removed from the system, once again disrupting the subscriber's telephone service. Additionally, during the process of reconnecting pair gain system 10 back to cross connect block 20, there is always the chance that a mistake could be made, resulting in an improper connection to exist. This can lead to subscriber 30 going without telephone service for an extended duration until the problem can be corrected.